Development of New Fe-based Shape Memory Alloy (Fe-Ni-Co-Ti Alloy)

1.适当时效的Fe-Ni-Co-Ti合金产生了完全孪晶的薄片马氏体相。通过调整化学成分和热处理条件，薄马氏体的热滞效应发生了很大的变化，并且无论热滞的程度如何，这些薄片马氏体都会产生完美的形状记忆效应。例如，当Fe-33Ni-10Co-4Ti合金在973K保温18K时，形成了ms和Af温度低于室温的热弹性马氏体，并在77K变形后加热到室温时产生了完全的形状记忆效应。对于Fe-31Ni-10Co-3Ti合金，在873K保温3.6K时，形成了具有较大热滞的薄片马氏体(即ms 200K，As 350K，Af 500K)。该样品在室温下完全为奥氏体态，在接近或低于MS的温度下变形后在Af以上加热，表现出完全的形状记忆效应。…更多的IMEN在室温下变形时几乎不会表现出形状记忆效应。然而，当试件一次冷却到液氮中产生大量马氏体时，即使在室温下变形，也会产生几乎完全的形状记忆效应。研究发现，Fe-Ni-Co-Ti合金的形状记忆效应在从低温到高温的较宽温度范围内通过热滞程度的变化表现出一定的特点。在Fe-Ni-Co-Ti合金中添加B或Al可以改善奥氏体形变后的塑性。这是由于抑制了沿奥氏体晶界析出的相所致。当Fe-33Ni-10Co-4Ti合金的马氏体热弹性在273K到77K之间热循环时，热滞变得明显大，即ms温度略有下降，Af显著增加。经过几次热循环后，Af温度上升到室温以上，加热到室温后仍有一定量的马氏体存在。因此，通过转变，板形恢复率从100%降至60%左右。较少

1. The properly ausaged Fe-Ni-Co-Ti alloys produce a thin plate martensite which is completely twinned. The thermal hysteresis of thin martensite is widely changed by the adjustment of chemical composition and the ausaged condition, and these thin plate martensites cause a perfect shape memory effect irrespective of the extent of the thermal hysteresis. For example, when Fe-33Ni-10Co-4Ti alloy is ausaged at 973K for 18ks, the thermoelastic martensite whose Ms and Af temperature are below room temperature is formed and the complete shape memory effect occurs during heating up to room temperature after deformation at 77 K. In the case of Fe-31Ni-10Co-3Ti alloy ausaged at 873K for 3.6ks, thin plate martensite with a large thermal hysteresis (i.e., Ms 200K, As 350K, Af 500K) is formed. This specimen which is fully austenitic at room temperature shows a complete shapememory effect when specimen is heated up above Af after the deformation at temperatures near or below Ms. The as-ausaged spec … More imen hardly exhibits the shape memory effect when deformed at room temperature. However, when the specimen is once subzero cooled to liquid nitrogen to produce a large amount of martensite, the almost complete shape memory effect occurs even by the deformation at room temperature. It has been found to be characteristic that the shape memory effect in Fe-Ni-Co-Ti alloys occurs over the wide temperature range from low temperature to high temperature by the change in the extent of thermal hysteresis.2. The ductility of austenite after ausaging is improved by the addition of B or Al to Fe-Ni-Co-Ti alloys. This is due to the suppression of precipitation of phase along austenite grain boundaries.3. When the thermoelastic martensite in Fe-33Ni-10Co-4Ti alloy is thermally cycled between 273K and 77K, the thermal hysteresis becomes markedly large, i.e., the Ms temperature is slightly decreased and the Af is markedly increased. After several thermal cycles, the Af temperature is raised above room temperature and the some amount of martensite remains even after the heating up to room temperature. Therefore, the degree of shape recovery is decreased from 100% to about 60% by the transformation. Less